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G. E. SG'RIBNE-R. TESTING AP?ARATUS PORiMULTIPLE SWITGHBOARD SYSTEMS.

No, 491,250. Patented Feb. 7, 189% [flan E5 55512117172). (5% MM g wwm m: cams pm'zas co, m-mrnumo" wnmuoms, o c.

unrest CHARLES E. SCRIBNER, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE \"VES'IERN ELECTRIC COMPANY, OF SAME PLACE.

TESTlNG APPARATUS FOR MULTiPLE-SWITCHBOARD SYSTEMS- SPEGIFIGATION forming part of Letters Patent No. 491,250, dated February 7, 1893. Application filed September 9, 1390. Serial No. 364%142. (N0 model.)

To (d5 scheme it may concern.-

.Be it known that 1, Onnnnns E.SOB1BNER, a citizen of the United States, residing at Chicage, in the county of Cool: and State of Illinois, have invented a certain new and useful Improvement in Testing Apparatus for Multiple-Switchboard Systems, (Case No. 192,) of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

My invention relates to telephone exchange systems in which multiple switch boards are employed.

The object of my invention is to simplify the apparatus whereby an operator at one board determines whether or not a line is busy at any other board.

Briefly then my invention relates to the busy test apparatus and consists in placing a battery in connection with that strand of the cord which connects with the sleeve thereof, a winding of the clearing out annunciator being preferably included to circuit with the said test battery. In this manner I avoid the use of a retardation coil and the loss of chicient current strength necessarily resulting from the use of such retardation coils. In other words the clearing out annunciator is made to perform its own function and in addition permits the test battery to be applied in a ground branch without destroying the balance as between the two sides of a metallic circuit.

Myinvention herein is an improvementu pon tors that the current from the test battery cannot harmfully affect the talking circuits.

In the accompanying drawings-Figure 1 is a diagram illustrative of three telephone lines connected with three multiple switch boards together with the operators outfits at two of the boards embodying my invention. Fig. 2 is a detailed View illustrative of the manner of winding the clearing out annunciators.

As shown in Fig. 1 station 1 is connected by metallic circuit a, with the centraloffice. Thus limb to of this metallic circuit extends from telephone switch at said station 1 through the spring and contact of each of the switches Z) c d of the line on the different boards and thence through individual annunciator e to the return portion or limb a of metallic circuit a. This limb a is connected with the test pieces or rings of the switches b c d and extends back to station 1 as shown.

Station 2 is connected by ground wire fwith switches b c d and through individual annunciator c and thence to ground. The test wire f of line fis connected with the rings or test pieces of switches b c d and through resistance f to ground.

Station 3 is connected by metallic circuit 9 with switches 71 0 (1 The limb g extends through the spring and contact of each of said switches and thence through individual annunciator c and thence to thelimb or return wire 9 of said metallic circuit g. This limb g is connected with the rings or test pieces of switches b c d and extends to stat-ion 3 after the manner described with respect to the circuit of station 1.

It will be noted that a usual subscribers outfit will be provided at station 2; the outfit at station 3 may be the same as illustrated at station 1.

I have shown the key board apparatus at the first and last of the switch-boards, and will briefly describe this outfit as shown at the first board. The loop plugs h and h are of usual construction. The tips of these plugs are connected with one strand of the cords and the sleeves of the two plugs are connected together by the other strand of the cords. The clearing out annunciator 1 is provided with two windings as shown in Fig. 2. Two branches Z from the different strands of the cords extend through the windings of this annunciator to ground. The branch from the strand connecting the sleeves together is connected through the test battery m. The branch Zfrom the strand connecting the tips of the plugs extends through the other winding of the clearing out annunciator directly to ground. The annunciator will therefore be operated either by current sent from the generator of the metallic circuit or by current sent from a grounded circuit as circuit f. The windings 7c and l are of such direction that when current is sent from a metallic circuit both coils will act to gether to energize and hence throw down In case of current sent from a grounded line as line fcoil Zalone will be included in the circuit but this will the clearing out shutter.

be sufficient to operate the insulator. It will .be noted that the battery m is always pres-- cut at the strand of the cords connecting the said l inef and throwing up cam lever of telephone switch 0 bring her telephone into conncction with subscriber at station 2 and will receive the subscribers order. Suppose the order be for connection with station 1. The

operator will first test circuit 'aof station 1.

This test consists of touching tip of plug 19 to test ring of switch d and listening at telephone. If no sound is heard the operator will know .that the line tested is free. She will then insert plug 19 as shown completing the connection and will then signal subscriber 1 by calling key q the calling current finding circuit from the calling generator to the lower contact point of key q, thence to the strap thereof, thence to the tip of the plug p, to the line spring of jack (1, through spring jacks c and b to substation 1, and through the signal bell and generator thereat; thence it returns over the line a to the sleeve of plug 19, thence through one winding of the clearing-out drop, to earth. Suppose, however, the telephone line had been busy when the test was made; that is, suppose plug it at the first board had been inserted in switch Z). In such case the subscriber at the last board 011 touching tip of plug 1) to test ring of switch (1 would hear the busy click in her telephone due to current from test battery m. I will trace this supposed test circuit from battery m. Beginning at ground the circuit would extend through battery on, through winding 7; to

strand of cord connecting with sleeve of plug h. Sleeve of plug h being connected with test piece of switch Z) the circuit of battery would be completed to limb a of circuit a and thence also to test piece of switch (I to which the tip of plug 1) is supposed to be applied. From the tip of plug 1) the circuit would be completed through the strand connecting with said tip as shown to spring rof the operators switch 0 and thence the cam lever being up through the telephone and thence to ground. A dummy telephone set 5 is shown connected between the contact of spring r and the ground branch of said operators outfit for the purpose of balancing the two sides of the circuit. Thus if any line is busy when a test is made at another board battery current will be found present and will cause the characteristic click or sound in the telephone of the operator making the test.

It will be seen that each of the coils of the clearing out annunciator will be connected in a branch from a different side of the metallic circuit so that the proper balance between the two circuits will be preserved while either of two connected subscribers may by turning his generator operate the clearing out annunciator. Thus, supposing subscriber at station 1 to operate his generator, the current would find circuit over lines a, 50 to the eX- change, and thereat to the tip and sleeve strands, respectively, of plug 19, and then through the respective windings of the clearing-out annunciator to earth.

Having thus described my invention I claim as new and desire to secure by Letters Patent:-

1. The combination with the pair of loop plugs and cords of a branch from that strand of said cords connecting the sleeves thereof, said branch extending through a winding of the clearing out annunciator and a battery to ground.

2. The combination with the clearing vout annunciator of two windings placed thereon, a pair of loop, plugs and cords connecting like parts thereof one of said windings being connected in a circuit branched from the strand of the cord connecting the sleeves and through a test battery to ground, the other winding being connected in a branch from the cord connecting the tips of the plugs and directly to ground and the switches connected with the subscribers lines, whereby the lines may be connected together and a test provided without disturbing the electrical balance of the lines.

3. The combination with aclearing out ancircuit, whereby the subscriber may operate 10 said clearing out annunciator, substantially as and for the purpose specified.

In witness whereof Ihereunto subscribe my name this 20th day of June, A. D. 1890.

' CHARLES E. SORIBNER. Witnesses:

ELLA EDLER, GEORGE P. BARTON. 

